1. Field of the Invention
The present invention relates to signal processing, and more particularly to a Doppler compensated signal processor for processing acoustic PSK messages.
2. Description of the Prior Art
Prior underwater test ranges used vehicles which transmitted a tone burst signal to provide location information and which did not transmit telemetry data. A high signal-to-noise ratio signal was required in order to detect a threshold level on the envelope of the tone burst signal to provide a time mark for determining range and direction information for tracking, and the time mark would not be generated at the same point of the envelope from signal to signal resulting in tracking errors. Also, since all vehicles generated the same tone burst signal, it was not possible to differentiate between multiple vehicles.
To provide more accurate tracking data and to provide vehicle identification, status and telemetry data, a PSK synthesizer was developed (see co-pending application Ser. No. 900,211 by Alan L. Lindstrum entitled "A PSK Pulse Synthesizer" filed Apr. 26, 1978) to convert the vehicle acoustic transmitter from a tone burst generator to a PSK message generator to provide vehicle identification, status and telemetry data. Since any change in the frequency of the PSK message due to Doppler shifts will introduce an error in the tracking data, a Doppler compensated PKS signal processor was required.